1. Field of the Invention
The present invention relates to a radiographic intensifying screen (hereinafter referred to simply as an "intensifying screen"). More particularly, the present invention relates an intensifying screen excellent in sharpness and durability, which has a protective layer formed by coating a solution containing a protective layer-forming resin.
2. Discussion of Background
An intensifying screen is used in intimate contact with an X-ray photographic film in order to improve sensitivity of photographing in the field of medical radiography for medical diagnosis or of industrial radiography for non-destructive inspection of materials.
Particularly, in the radiographic diagnosis, it is strongly demanded for accurate diagnosis to improve sharpness of an intensifying screen. Thus, it is studied to improve image quality of an intensifying screen, for example, by reducing a binder resin amount in a fluorescent layer. However, in the case of forming a protective layer by coating a solution containing a protective layer-forming resin (hereinafter referred to as a "protective layer coating solution") on the surface of a fluorescent layer, if the binder resin amount is small in the fluorescent layer, it has been difficult to obtain an intensifying screen having a satisfactory protective layer excellent in durability and uniform film properties, due to such problems as that a protective layer coating solution penetrates into the fluorescent layer during coating and that bubbles are sometimes generated in the fluorescent layer. On the other hand, a large amount of a protective layer coating solution is coated by considering the penetration of the protective layer coating solution into the fluorescent layer, there has been a problem of degrading sharpness of the intensifying screen. Thus, in the intensifying screen having a protective layer formed by coating a protective layer-forming solution, it has been difficult to improve durability and sharpness at the same time by maintaining the binder resin amount in the fluorescent layer sufficiently small.
An object of the present invention is to provide an intensifying screen having improved sharpness and satisfactory durability and a process for preparing the same, which comprises forming a protective layer by coating a protective layer coating solution on the surface of the intensifying screen while maintaining the binder resin amount in the fluorescent layer sufficiently small and preventing the protective layer coating solution from penetrating into the fluorescent layer.
In order to image quality properties of an intensifying screen, the present inventors have variously studied to overcome the above-mentioned problems of the penetration of the protective layer coating solution into the fluorescent layer and the generation of bubbles in the fluorescent layer when the binder resin amount in the fluorescent layer is reduced. As the results of this study, it has been discovered that an intensifying screen having excellent sharpness and durability can be obtained without penetration of a protective layer coating solution into a fluorescent layer or without generation of bubbles in a fluorescent layer in the case of forming a protective layer on the fluorescent layer with a reduced binder amount, (i) by providing a water repellent layer on the fluorescent layer and then coating a protective layer coating solution thereon, (ii) by providing a fluorescent layer containing a water repellent and then coating a protective layer coating solution on the fluorescent layer, or (iii) by coating a small amount of a solution containing a resin and an organic solvent (hereinafter referred to as a "resin solution") on a fluorescent layer to provide a resin layer thinner than a protective layer and then coating a protective layer on the resin layer.